Patent Literature 1 (Japanese Unexamined Patent Application Publication No. 2008-084174) describes one method for inspecting printed matter including multiple patterns of, for example, characters and images. With this method, a predetermined area of an image is set as a common data area and another predetermined area of the image is set as a character data area. A reference common data pattern for the common data area and a reference character data pattern for the character data area are generated from a reference image and are stored. For an inspection target image, the method extracts a partial image forming a common data area and a partial image forming a character data area. The partial image for the common data area is compared with the corresponding reference common data pattern, and the partial image for the character data area is compared with the corresponding reference character data pattern to finally determine the correctness of the printed matter. Such matching in divided areas of an image improves the efficiency of inspection.
However, an inspection target may include a plurality of different objects that are printed or inscribed close to one another. For example, a symbol such as a barcode may include numbers or characters printed close to one another for the convenience of users. Misalignment during transportation of such an inspection target on a conveyor line can cause a specified area of an image to erroneously contain a plurality of objects. This may result in the erroneous extraction of objects.